29 mpg to 24 mpg drop

[david_ES2]

Maybe cause a/c is on

 

[i_hate_autofraud]

I'd do a fresh ODBII scan but with a premium scanner. The cheap scanners only tell you the codes that set the engine light.

For a detailed 'deep' scan for OEM detailed codes for the engine AND the transmission.

A pal had the same MPG problem, turns out he had a transmission temp sensor performance problem that disabled the Torque converter lockup even at high way speeds! Ya never know til ya look!!

 

[Kuato]

Originally Posted By: david_ES2
Maybe cause a/c is on


That's a big one. Run it just a little around town and it will suck the gas.

 

[THORROMIG]

Good suggestions, I would run back to back Techron Fuel System Cleaner fills. Them NGK Iridiums are not gonna hurt your fuel mileage a bit. AC will put a huge hit on MPGs in no time & tis the season for it!!

 

[i_hate_autofraud]

If you're concerned the A/C is still on, not only turn off the A/C dash controls but visually check if the a/c clutch is disengaged while the engine is idling. Any defect in the dash electrics could keep it on!

 

[Jarlaxle]

Originally Posted By: AZjeff
Originally Posted By: Powerglide
Summer gas bland.


Thought winter blend lowers mileage. Can't be both.


Won't be THAT big a drop (the OP's is 20+%), but I recall some places use E10 only in summer.

 

[MrQuackers]

A good mod would be one that only allows the AC while in DFCO

 

[circuitsmith]

Was wheel alignment checked?
Recently correcting for toe 0.2 deg off increased 1 mpg.
To check for a dragging brake cruise a few miles on a road where you can coast down with minimal braking.
Then get out and feel the wheels for one hotter than the others.